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[Update: An official with the U.S. Fish and Wildlife Service contacted ReWire August 31 to clarify the agency's position on assessment of solar power tower projects. FWS's Assistant Regional Director for External Affairs Paul McKim told ReWire that FWS is not asking for a moratorium on solar power tower projects, but merely urges its fellow agencies to proceed with caution in approving such projects until more research is done on their effect on wildlife. McKim conceded that Sorensen's suggestion that more data be collected on wildlife impacts "before approving more projects" could be read as a suggestion for a moratorium, but said that was not FWS' intent. Sorensen's letter has since been removed from the California Energy Commission website.]

An official with the Palm Springs office of the U.S. Fish and Wildlife Service (FWS) has suggested that the California Energy Commission (CEC) and other agencies involved in approving desert renewable energy facilities allow "at least a couple years" of research on already-approved concentrating solar power tower facilities before approving any new projects of that design, or at least limiting new approvals until the studies are done.

The suggestion was made in a letter [since removed from the CEC website -- see update above] from Pete Sorensen, Division Chief of the FWS's Palm Springs office, attached to a list questions regarding potential threats to bird and bat species from two projects planned by BrightSource Energy, the Hidden Hills and Rio Mesa solar projects in Inyo and Riverside counties. That letter was made public on the CEC's website today.

Both the Rio Mesa and the Hidden Hills sites have been identified as significant bird areas. Each of the projects would surround 750-foot tall towers with tens of thousands of mirrored heliostats, which would focus sunlight on boilers atop the towers to generate heat that would drive power-generating turbines. The potential threat to flying animals comes from the intense radiation near the towers, termed "solar flux," which some wildlife biologists fear may injure or kill wildlife through blinding, burns, or even incineration.

The concern is motivated in part by earlier studies of bird mortality at the now-decommissioned Solar One power tower facility at Dagget, where biologists found a significant number of burn injuries among birds found dead on the site. (Collisions with mirrors accounted for more injuries than burns, though that's hardly reassuring news.)

According to the letter from Sorensen,

We are concerned about the increasing number of power tower projects that are proposed or undergoing permitting review, given the outstanding questions about the impacts of utility-scale application of this technology. As such, it would be beneficial to the permitting process for pending and future projects, including Hidden Hills and Rio Mesa, to gather monitoring data that answer some of the questions about avian physiological tolerance and behavioral response to power towers, from already approved projects, before approving more projects. Increasing our knowledge about potential impacts from this technology would further our ability to complete science-based analyses of direct, indirect, and cumulative effects to the avian community, as required by our joint public trust responsibilities. Therefore, we suggest that the Agencies limit the number of power tower projects that are considered for permitting and development until we obtain a more detailed understanding of this technology and its impacts, based on at least a couple years of scientifically robust monitoring. Deploying technology of this scale in multiple places and on a short timeframe without such an understanding compromises our ability to make informed decisions on projects that would permanently and cumulatively impact species and the extensive tracts of desert habitat upon which they depend. [Emphasis added.]

Most active solar power tower proposals in the U.S. have not yet been approved. ESolar's Sierra SunTower in Lancaster is now in operation. BrightSource's Ivanpah Solar Electric Generating System is under construction in the California desert south of Las Vegas, as is Solar Reserve's Crescent Dunes project near Tonopah, NV. The CEC and BLM have each approved another SolarReserve solar power tower project at Rice, California, east of Joshua Tree National Park, but construction has not yet commenced on that project.

FWS's questions were provided to BrightSource and the CEC on August 28 as part of the wildlife agency's participation in a workshop on the potential effects of solar flux at the Hidden Hills and Rio Mesa sites.

Our technology has been specifically designed to avoid harming birds. Unlike older technology, when our mirrors are not focused at the top of the tower, the light is focused in a diffuse ring around the top of the tower, at concentration levels too low to have any detrimental effect on birds. We have also reduced the size of the heliostats and placed them lower to the ground to avoid collisions, and we avoid siting projects adjacent to actively farmed and irrigated agricultural land or standing water that might attract insects and birds.

In FWS's written set of questions posted today by CEC, FWS implies that BrightSource has not backed up those assertions sufficiently to satisfy the agency's scientists.

The Service is concerned about the potential impacts of flux associated with solar power tower technology on species protected under the Endangered Species Act, Migratory Bird Treaty Act, and the Bald and Golden Eagle Protection Act. We request that BrightSource provide sufficient and scientifically robust data to validate their assertion that avian and bat species will not be impacted by this technology.... data thus far provided by BrightSource are insufficient to assess project impacts on avian and bat species.

A moratorium on new power tower approvals could affect the Hidden HIlls and Rio Mesa projects, as well as the Palen Solar Power Project recently acquired by BrightSource.

For ongoing environmental coverage in March 2017 and afterward, please visit our show Earth Focus, or browse Redefine for historic material.
KCET's award-winning environment news project Redefine ran from July 2012 through February 2017.

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